Crossbar switch



May 20, 1969 R. P. HOLTFRETER ET AL 3,445,795

CROS SBAR SWITCH Sheet I of 7 Filed Oct. 2. 1967 R. 1-? HOL TFRETER WVENTO H. E. Mc CULL OUGH ATTORNEV y 969 R. P. HOLTFRETER ETA!- 3,445,795

CROS SBAR SWITCH Sheet 8 of7 Filed Oct. 2, 1967 N 0: Rk Q:

May 20, 1969 P. HOLTFRETER ET AL 3,445,795

CROSSBAR SWITCH Filed Oct. 2, 1967 Sheet of? R. P. HOLTFRETER ET CROSSBAR SWITCH Filed on. 2. 1967 Sheet 5 of "7 R. P. HOLTFRETER ET AL 3,445,795

May 20, 1969 CROSSBAR SWITCH Sheet Filed Oct. 2, 1967 FIG. 9

1969 R. P. HOLTFRETER ET AL 3,445,795

CROSSBAR SWITCH Sheet Filed Oct. 2 1967 FIG. /2

United States Patent O 3,445,795 CROSSBAR SWITCH Richard P. Holtfreter, Pickerington, and Harold E. Mc-

Cullough, Hilliard, Ohio, assiguors to Bell Telephone Laboratories, Inc., Murray Hill and Berkeley Heights, N.J., a corporation of New York Filed Oct. 2, 1967, Ser. No. 672,071 Int. Cl. H01h 67/14, 67/02, 63/02 US. Cl. 335-112 23 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention relates to magnetically operated switches of the crossbar type.

Description of the prior art Broadly, the function of a crossbar switch is to establish an electrical path between one or more conductors in one group and one or more conductors in another group. In general, the connecting function is performed through the interaction of mechanisms commonly called select units and hold units. Both kinds respond to electromagnetic stimulation; the select units to isolate conductors to be interconnected and the hold units to interconnect the isolated conductors.

The conductors to be interconnected are terminated on opposite contacts of a contact pair. The contact pairs, in turn, are collected into sets to form crosspoints. The crosspoints are contained in the hold units and each hold unit generally has ten crosspoints.

Each crosspoint opens and closes in response to card movement. More particularly, each hold unit has an armature and one or more cards arranged to reciprocate in response to movement of the armature. When moved in one direction, each card opens a crosspoint and, when moved in the other direction, closes the crosspoint. Card movement, however, is selective and only occurs when the card has been preconditioned for movement by a finger.

Each card is associated with a finger. The finger reciprocates between two positions in response to select unit operation. In the first position, the finger fits in an operate zone located between the hold armature and a card. As a result, when the hold armature moves, the finger bears against the card, the card moves and the condition of the crosspoint controlled by the card and finger changes. Thus, a card is preconditioned to move when the finger is in the first position.

In the second position, the finger is not in the operate zone. Consequently, when the hold armature moves, the finger fails to bear against the card, the card does not move and the condition of the associated crosspoint remains unchanged.

Thus, the fingers respond to the select units to precondition cards for operation, while preconditioned cards respond to the hold units to operate crosspoints. In short, the cards and fingers comprise an interface between the select units and the hold units which translates various combinations of hold unit and select unit operation into operation of specific crosspoints.

Crossbar switches of the type described are found everywhere in the communications industry. Of the thousands of telephone central offices, for example, each uses hundreds. With such a heavy usage, there is a tremendous demand for improvement.

Manufacturing efficiencies are avidly sought. In view of the great numbers, small manufacturing economies produce large net savings. Operating efliciencies are similarly desirable. Faster operation, lower power requirements, and easier maintenance all mean substantial overall operating cost savings. Finally, it is advantageous to reduce the amount of space required to accommodate the switch itself. With smaller size, more switches can be installed in available mounting equipment, thus reducing the expenses of switch users.

Broadly, it is the object of this invention to improve the construction and operation of crossbar switches.

SUMMARY OF THE INVENTION According to this invention a plurality of hold units comprising components designed for compactness, separate fabrication, and efiicient operation are detachably mounted on a frame in cooperating relationship with a plurality of detachably mounted select units.

According to one feature of this invention, each hold unit includes a hold magnet assembly and two meshing contact assemblies adapted to be snapmounted on the hold magnet assembly.

According to another feature of this invention, one contact assembly includes fixed contacts and the other contact assembly contains contacts fabricated from pretensioned wire springs.

According to another feature of this invention, each hold magnet assembly includes a plurality of rotatably mounted U-shaped finger units.

According to still another feature of this invention, each U-shaped finger unit is doubly biased; one bias urging the open ends of the finger unit together and one bias urging the open ends of the finger unit in a predetermined direction.

According to still another feature of this invention, each hold unit includes a plurality of cards wherein each card has an aperture for receiving one end of a finger unit and a plurality of openings for collecting a plurality of contacts into a crosspoint.

According to another feature of this invention, each hold unit includes an armature and a rotatably mounted bracket for regulating armature movement.

According to yet another feature of this invention, the frame includes a plurality of tapped holes and apertures and each select unit includes a threaded core and a notched bobbin which cooperate with each other and the tapped holes and apertures in the frame to detachably join the select unit to the frame.

A better understanding of these and other features of this invention will be aided by the following detailed description when taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partial front view of a crossbar switch assembled in accordance with this invention;

FIG. 2 is a front view of a hold unit assembled in accordance with this invention;

FIG. 3 is an end view of the hold unit illustrated in FIG. 2;

FIG. 4 is a partial top view of the hold unit illustrated in FIG. 2;

FIG. 5 is a partial perspective view of the hold unit illustrated in FIG. 2;

FIG. 6 is an enlarged perspective view of portions of two cards, wire springs, a finger unit, an operator, an armature and balance springs for holding the cards in position;

FIG. 7 is a perspective view of a stop bracket for regulating armature movement in a hold unit;

FIG. 8 is a perspective view of a U-shaped finger unit;

FIG. 9 is a side view of a U-shaped finger unit;

FIG. 10 is a perspective view of a bobbin adapted for use in a select magnet assembly;

FIG. 11 is an enlarged section view of a portion of the frame showing a select magnet assembly partially in section mounted thereon; and

FIG. 12 is a side view of a portion of a frame on which select magnet assemblies shown fully and in section are mounted.

DETAILED DESCRIPTION Turning now to FIG. 1, a crossbar switch is disclosed which comprises a frame 21, a plurality of hold units 40, and a plurality of select units 100. The hold units 40 and the select units 100 cooperate to interconnect conductors, while the frame 21 serves as a support for joining the hold units 40 and the select units 100 in a working relationship.

The frame 21 comprises two metallic siderails 22 and two metallic end sections 23 and 24, respectively. The two siderails 22 and the two end sections 23 and 24 are joined, advantageously by welding, to form an open frame. Each siderail 22 includes a plurality of notches 25 for accommodating portions of the hold units 40, while the end sections 23 and 24 are adapted to accommodate portions of the select units 100.

The end sections 23 and 24 are advantageously fabricated from flat stock. As shown in FIGS. 1 and 12, each includes a portion 26 adapted to receive several adjusting screws 27 and a portion 28 containing apertures 29 and tapped holes 30. As will be described hereafter in more detail, the screws 27, the apertures 29 and the tapped holes 30 cooperate to join the select units 100 to the frame 21. Finally, each end section 23 and 24 includes one or more holes 31 for mounting the frame 21 on a suitable support, such as a relay rack.

Turning now to the hold units 40, as shown in FIGS. 2, 3, 4 and 5, each comprises three discrete subassemblies, viz, a hold magnet assembly 41, a moving contact assembly 42 and a fixed contact assembly 43. The two contact assemblies 42 and 43 mesh with each other and serve as terminals for conductors which are to be selectively interconnected; the fixed contact assembly 43 containing a plurality of individual fixed contacts, and the moving contact assembly 42 containing a plurality of moving con tacts arranged in sets, or crosspoints, and disposed to interact with the fixed contacts on a two-for-one basis. The hold magnet assembly 41 supports the two contact assemblies 42 and 43 and cooperates with the select units 100 to isolate and operate crosspoints. The following paragraphs describe in detail the components in each of the three subassemblies.

As shown in FIG. 5, the hold magnet assembly 41 includes a support plate 46, a motor unit 47, an armature 48, a stop bracket 49, mounting posts and a plurality of finger units 51. The support plate 46 is advantageously made from flat metal stock and serves to support the other components. It includes two sets of projecting ears 52 and 53, respectively, and a pair of mounting holes 54. The ears 52 and 53 are located on one end of the support plate 46 and the holes 54 are in the other end. The ears 52 engage notches 25 (FIG. 1) on the frame 21 and portions of the armature 48, while the cars 53 cooperate with a pair of mounting holes (not shown) to hold the fixed contact assembly 42 on the support plate 46. The mounting holes 54 aid in holding the moving contact assembly 42 on the support plate 46.

As shown in FIG. 3, the motor unit 47 and the stop bracket 49 are mounted on opposite sides of the support plate 46 with the armature 48 in between. The motor unit 47 is conventional and includes a core 56 surrounded by a coil wound bobbin 57. The core 56 delivers electromagnetic energy for activating the armature 48.

As shown in FIG. 5, the armature 48 comprises two flat sections 58 and 59 joined at an obtuse angle. The flat section 58 fits between the stop bracket 49 and the core 56. It is made of a magnetic material such as low carbon steel and is notched at one end to rotatably fit over one ear 52. A narrow bar, or web, 61 extends between the portion containing a button 60 and the notched end portion and is superimposed over the finger units 51.

The button 60 is conveniently made of a plastic material such as acetal resin. As shown in FIG. 4, it engages a return spring 64 mounted on the support plate 46. The return spring 64 is advantageously a piece of nickel silver snap-mounted in place by one end. The other end bears against the button 60 and urges the armature 48 toward its rest position. If desired, off-normal contacts can readily be combined in a conventional manner with the return spring 64 to indicate the operating condition of the crossbar switch 20.

Referring to FIGS. 4, 5 and 6, the armature 48 rotates between the face of the core 56 and the stop bracket 49. The stop bracket 49 holds the armature 48 in position and regulates the amount of travel. As best seen in FIG. 7, the stop bracket 49 is a metallic member which includes two arms 65 and 66, an elongated mounting hole 67 and a slot 68. As shown in FIG. 4, the support plate 46 includes a tapped hole 70 and a pin 71. When the stop bracket 49 is mounted, the pin 71 fits in the slot 68 while a bolt 72 extends through the elongated mounting h le 67 and into the tapped hole 70 to hold the stop bracket 49 in position on the support plate 46.

The arms 65 and 66 on the stop bracket 49 regulate travel and hold the armature 48 in place, respectively. In order to modify the amount of armature travel, for example, the bolt 72 is loosened and the stop bracket 49 is rotated about the pin 71. When the arm 65 is moved closer to the armature 48, movement is reduced. When it is moved farther away, armature movement is increased. In either event, however, there is little interference with the holding function of the arm 66.

As can be seen in FIG. 7, the arm 66 is disp sed on a radial line passing through the portion of the slot 68 which accommodates the pin 71. As a result, when the stop bracket 49 is rotated to change the position of the arm 65 relative to the armature 48, very little change occurs in the spacing between the arm 66 and the armature 48. Thus, changes in armature travel are readily obtained without adversely affecting the positioning function of the arm 66.

As can be seen in FIG. 5, the remaining components of the hold magnet assembly 41 are the mounting posts 50 and the finger units 51. The mounting posts 50 are aflixed to the support plate 46 and each includes a groove 72. The finger units '51 are generally U-shaped and each attaches to a mounting post 50.

As shown in FIG. 8, each finger unit 51 includes two legs 73 and a bight 74. The bight 74 of each finger unit 51 snaps into a groove 72 and is free to rotate around the post 50. As can be seen from FIGS. 8 and 9, the legs 73 are double-biased. As shown in FIG. 8, the legs 73 are deformed so as to be urged together at the free ends. As shown in FIG. 9, both legs 73 are deformed so as to be urged in a predetermined direction; specifically, away from the support plate 46 as shown in FIG. 3. The double bias targets the legs 73 with respect to other components and thereby simplifies the assembly of the hold magnet assembly 41 and the moving contact assembly 42.

The moving contact assembly 42 is the second subassem'bly of each hold unit 40 and, as best seen in FIG. 3, comprises twin wire contact assemblies 76, cards 77, an upper balance spring 78, a lower balance spring 79 and a clamp 80. The twin wire contact assemblies 76 all contain a base 81 and a plurality of wires 82. Each of the wires 82 includes a contact 110. Furthermore, the wires 82 are made from a spring material such as cupro-nickel and are kinked or otherwise deflected so as to exert a force in a common direction. The contacts 110 are electrically conducting and are advantageously made of palladium. All of the wires 82 are embedded in the bases 81. Each base 81 is advantageously made of a plastic material such as phenolic resin and each is adapted to cooperate with other bases 81 to form a stack.

Referring to FIG. 6, the cards 77 are advantageously made of a plastic material such as nylon and each is adapted to accommodate a leg 73 of a finger unit '51 and and to collect the wires 82 into cont-act sets. Each card 77 includes an aperture 85, holes 86 and an ear 87. Each hole 86 has a wide portion and a narrow portion. The narrow portion includes two spaces divided by a boss 88. The holes 86 receive a pair of wires 82 through the wide portion and align them side by side on either side f the boss 88. As can be seen in FIG. 3, the deflection of the wire 82 urges them into the spaces between the boss 88.

In the embodiment illustrated, each card 77 has six holes 86. Consequently, each crosspoint associated with a card 77 is of the six-wire type. In other words, each crosspoint contains six contact pairs and can interconnect six wires. 'It will be readily apparent, however, that other crosspoint multiples can easily be obtained simply by varying the number of holes 86 and increasing or decreasing the number of wire contact assemblies 76 as required.

The apertures 85 accommodate the legs 73 of the finger units 51. Each has a shallow section 89 and -a deep section '90. As shown in FIG. 6, the cards 77 are mounted on the ends of the wire 82 in pairs; specifically, with the deep sections 90 of each adjacent. In other words, the cards 77 are mounted so as to appear as mirror images of each other.

Each aperture 85 is designed to accommodate a single leg 73. As a result, each finger unit 51 brackets a pair of cards 77. When the legs 73 are in position, as shown in FIG. 3, the double bias therein urges them against the sides of the apertures 85. Consequently, there is always a force of friction between the cards 77 and the finger units 51 which impedes free movement of the legs 73. Moreover, the double bias generally aligns the free end-s of the finger units 51 in a common plane. Thus, when the moving cont act assembly 42 'is attached to the hold magnet assembly 41, the legs 73 are easily inserted into the apertures 85 in the cards 77 The cards 77 are positioned adjacent to the ends of the wires 82 by the upper and lower balance springs 78 and 79, respectively. Specifically, each upper spring 78 engages an ear 87 on a card 77, while each lower balance spring 78 extends through a hole 86. As best seen in FIG. 6, the end of each lower balance spring 79 contains two notches 112. Moreover, one hole 86 in each card 77 includes a slot 113 in the wide portion thereof. When the end of a lower balance spring 79 is inserted in a hole 86, it slides down into the slot 113 and the two notches 112 grip the card 77. Thus, the upper and lower balance springs 78 and 79 cooperate'to lock the cards 77 in position at the ends of the wires 82.

As can be seen in FIG. 3, the upper and lower balance springs 78 and 79 are biased to urge the cards 77 in a predetermined direction, viz., towards the support plate 46. Both springs are advantageously made of a spring material such as nickel silver.

As shown in FIG. 3, the wire contact assemblies 76 are stacked and, with the upper and lower balance springs 78 and 79, are held together by the clamp 80 to form the moving contact assembly 42. The clamp 80, however, also detachably joins the moving contact assembly 42 to the hold magnet assembly 41. The clamp is advantageously made of a metal such as nickel silver, and is formed into a U-shape. The open ends terminate in hooks 91. The hooks 91, as shown 'in FIG. 5, snap into the mounting holes 54 on the support plate 46 and locate the moving contact assembly 42 in a predetermined position with respect to the fixed contact assembly 43.

The fixed contact assembly 43 is the last subassembly of each hold unit 40 and, as shown in FIG. 3, includes contacts 92 which are adapted to engage the contacts 110 located on the wires 82 in the moving contact assembly 42. In addition to the contacts 92, the fixed contact assembly 43 includes terminal bars 93, support blocks 94 and clamps 95.

The support blocks 94 are advantageously made of a plastic such as polystyrene while the terminal bars 93 are made of electrically conducting metal strips such as nickel silver. The terminal bars 93 are embedded in the support blocks 94 to form a ladder-like structure. The ends of the terminal bars 93 extend through the support blocks 94 and serve as terminals to accommodate leadout wires. For facilitating attachment of the leadout wires, the ends of the terminal bars 93 contain loops. The contacts 92 are aifixed to one edge of the terminal bars 93. The contacts 92 are electrically conducting and are advantageously made of palladium. As shown in FIG. 2, the spacing of the contacts 92 is such that each is readily superimposed over a pair of contacts 110.

When the moving contact assembly 42 and the fixed contact assembly 43 are mounted in a hold unit 40, the wires 82 and the contacts 92 mesh. In the embodiment disclosed, the cards 77, under the influence of the upper and lower balance springs 78 and 79, deflect the wires 82 toward the bar 61. Consequently, the contacts 110 and the contacts 92 are separated by an airgap. As a result, the contact configuration in the disclosed embodiment is of the normally open type and utilizes card release operation.

Returning to the support blocks 94, in addition to aligning the terminal bars 93 in parallel planar relationship, they cooperate with the clamps 95 in making connection to the support plate 46. Each support block 94 includes a pin 96, as shown in FIG. 3, which engages a hole in a clamp 95. The clamps 95, in turn, terminate in hooks 97. The hooks 97 engage the ears 53 and mounting holes (not shown) and hold the support blocks 94 in position on the support plate 46.

The clamps 95 are advantageously made of metal such as nickel silver and, like the clamp 80 in the moving contact assembly 42, are U-shaped. By using clamps to mount the fixed contact assembly 43 and the moving contact assembly 42, maintenance and manufacture are simplified. For example, each assembly can be separately fab ricated and then mounted on the hold magnet assembly 41. Moreover, when contact failures or other operating problems occur, either or both can readily be removed and replaced.

Thus, the hold units 40 are readily assembled from several subassemblies. After assembly, the hold units 40 are easily mounted or demounted from the frame 21. As previously described, the cars 52 on the support plate 46 each engage a notch 25 on a siderail 22. As shown in FIG. 5, there is at least a third point of attachment for each hold unit 40; viz., a tab 98 which contains a bolt accepting hole. When mounted on the frame 21, the bolts through the tabs 98 firmly aflix the hold units 40 to the frame 21 while the ears 52 space each along the siderails 22 in positions suitable to cooperate with the select units 100.

As shown in FIG. 1, the select units 100 mount on the frame 21 between the end sections 23 and 24. Each select unit 100 includes a select magnet assembly 101 and a select bar 102. As shown in FIG. 11, each select magnet assembly 101 comprises a bobbin 103, a core 104 and a coil 105. The core 104 is made of a magnetic material such 7 as low carbon steel and one end is threaded to screw into a hole 30 in the end sections 23 or 24. The threaded end also includes a screwdriver slot, while the other end is slightly domed.

The coil 105 is conventional, but the bobbin 103, as shown in FIG. 10, terminates in a flange 106. The flange 106 is grooved to accommodate leadout wires and includes slotted tabs 107. The bobbin 103 is advantageously formed from a plastic such as nylon. When the bobbin 103 is installed on one of the end sections 23 or 24, the slotted tabs 107 fit through and around the apertures 29 to secure the bobbin 103 in place. Similarly, the core 104 fits through the bobbin 103 and engages the tapped hole 30. As a result, the core 104 lends rigidity to the bobbin 103 while retaining the ability to easily be adjusted in and out of its hole 30.

Each select bar 102 is made of a rigid material such as stainless steel, and, as shown in FIG. 1, includes operators 108 and an armature plate 109. The armature plates 109 cooperate with the cores 104 to rotate the select bar 102. Each armature plate 109, when its select bar 102 is mounted on the frame 21, is positioned adjacent to the domed ends of two cores 104. Normally, the cores 104 and the armature plate 109 are separated by an airgap. The size of the airgap affects operation and must be precisely regulated. In this case, the airgap is readily adjusted simply by screwing a core 104 into or out of its mounting hole 30 to bring it nearer or farther from the armature plate 109. Thus, precision airgap adjustments are readily made in the select units 100.

The select units 100 are alternately mounted on the frame 21. In other words, they are mounted so that adjacent armature plates 109 are separated by a select bar 102 having its armature plate 109 located at the opposite end section. Moreover, the select bars 102 are pivotally mounted. Each end, as shown in FIG. 1, engages a screw 27. Thus, when the armature plate 109 is attracted by the core 104 of one of the select magnet assemblies 101, the select bar 102 rotates. The select bar 102 is returned to its rest position after operation by the action of a conventional return spring arrangement (not shown).

The operators 108 extend outwardly from the select bars 102 and are distributed along one side. Each is rigidly attached to a select bar 102 and, as shown in FIG. 6, each terminates in a paddle-shaped end. When the select bars 102 are mounted on the frame 21, the paddle-shaped end of each operator 108 fits between the legs 73 of one finger unit 51.

The double bias of the finger units 51 aids in assembling the hold units 40 and select units 100 into the completed crossbar switch 20. Because of the bias, the legs 73 in one hold unit 40 project out from substantially the same place as in every other hold unit 40. As a result, corresponding legs 73 in each hold unit 40 will be aligned with each other when the hold units 40 are mounted on the frame 21. Consequently, it is quite simple to insert the ends of the operators 108 between each pair of legs 73 when the select bars 102 are being mounted.

Operation of the assembled crossbar switch 20 occurs in three steps. Release, however, requires only one. Broadly, the first operating step comprises the activation of a select unit 100. Activation of the select unit 100 predisposes for operation a single crosspoint in each hold unit 40. In the second step, a hold unit 40 is activated. Activation of the hold unit 40 operates the predisposed crosspoint which it contains. In the third step, the select unit 100 is allowed to return to its starting condition. In the release step, the hold unit 40 is merely deactivated.

More specifically, the first step begins when a select magnet assembly 101 is energized. As can be seen from FIG. 1, when the select magnet assembly 101 is energized, the armature plate 109 is attracted to one of the cores 104. As the armature plate 109 is attracted, it rotates a select bar 102. When the select bar 102 rotates, it rotates all of its operators 108. As shown in FIG. 6, when an operator 108 rotates, it pushes a leg 73 of a finger unit 51 from the deep section of a card 77 to the shallow section 89. The first step is completed when all of the legs 73 being pushed by the operators 108 have moved into the shallow sections 89.

The second step begins when the hold magnet assembly 41 in a selected hold unit 40- is energized. When the hold magnet assembly 41 is energized, the armature 48 moves by force of attraction towards the core 56. When the armature 48 moves, it presses the bar 61 against the legs 73- on all of the finger units 51 in the hold unit 40. As the bar 61 continues to press, the legs 73 are displaced. Those legs 73 which are in the deep sections 90 simply move unimpeded through the apertures 85. That leg 73, however, which is in the shallow section 89 presses against its associated card 77.

The card 77 pressed by the leg 73 moves in the same direction as the bar 61. As the card 77 moves, the wires 82 which it contains follow. The wires 82 move independently; e.g., in response to the force which has been pretensioned in each. As they move, and advantageously before movement of the card 77 ceases, the contacts 110 engage opposing contacts 92. Thus, a connection is established between the wires 82 and the contacts 92. This connection in turn interconnects the conductors which terminate on the contacts 92 and the wires 82. Step two is complete when the armature 48 ceases to move and thereby discontinues movement of all of the other components.

In the third step, the select magnet assembly 101 is deenergized. When the select magnet 101 is deenergized, the armature plate 109 and all of the operators 108 return to the starting position. When the operators 108 return to the starting position, all of the legs 73- except the one associated with the operated hold unit 40, return to their respective deep sections 90. The leg 73 associated with the operated hold unit 40, however, is held by the cooperating forces exerted by the hold bar 61 and the card 77. Thus, at the conclusion of the third step, one leg 73 does not return to its deep section 90 but remains in its shallow section 89.

The contacts 92 and the contacts 110 in the operated hold unit 40 remain in contact until the release step occurs. In the release step, the energized hold unit 40 is deenergized. When the hold unit 40 is deenergized, the armature 48, together with the card 77 and the legs 73, returns to the starting position under the urging of the return spring 64. The card 77 returns to the start position under the urging of the balance springs 78 and 79. As it returns, it carries the wires 82 thereby breaking the connection between the contacts 110 and the contacts 92. So ends the release step.

While an operated hold unit 40 cannot be deenergized without disrupting the union between the contacts 92 and the contacts 110, the select units may be activated or deactivated at any time. In fact, the select units 100 can even preselect crosspoints for operation in an operated hold unit 40 before the hold unit 40 is deenergized. For example, where a crosspoint is to be preselected, the appropriate select unit 100 is activated, Although the desired leg 73 cannot be moved from its deep section 90 to its shallow section 89 because of the impediment imposed by the bar '61, it nevertheless can be biased toward the shallow section 89.

When the hold unit 40 is deenergized, however, the bar 61 returns to normal and removes the impediment to movement of the biased leg 73. As the bar 61 returns to normal, two things happen. First, the card 77 holding the operated crosspoint returns to normal under the influence of the upper and lower balance springs 78 and 79 and allows the operated crosspoint to release. At the same time, the biased leg 73 moves from its deep section 90 into its shallow section 89. Upon reenergization of the hold unit 40, the bar 61 presses against the biased leg 73 which is now in the shallow section '89, lifts the associated card 77, and closes the new crosspoint.

While operation occurs in sequential steps, the friction forces developed between the leg 73' and the sides of the card 77 permit the first two steps to follow each other closely. In fact, the steps can follow each other so closely that the select units 100 and the hold units 40 can be operated almost simultaneously.

Because the legs 73 are always in contact with the sides of the cards 77, they are always subjected to a force of friction. The friction force opposes, or damps, any forces tending to set up vibration in the legs 73. Thus, when the select unit 100 operates, there is no need to provide a time interval for damping leg vibration which otherwise might cause false operation. Consequently, one step can follow the other without hesitation.

Furthermore, while the embodiment disclosed contains only five select units 100 and ten crosspoints per hold unit 40, other combinations are readily available. For example, it is a simple matter to add one or more select units 100 to the frame 21 and substitute hold units containing twelve or more crosspoints for the ten crosspoint-containing hold units which are disclosed.

:In summary, a new crossbar switch has been disclosed which has been assembled from discrete subassemblies. As a result, it is easily repaired in field installations and is eminently suited for mass production techniques. Furthermore, no delay is necessary between operating steps so it can be operated faster. Moreover, wire spring contacts are used which permit compact design and require less energy to open and close crosspoints. As a result, the new crossbar switch is smaller and requires less power to operate.

Only one embodiment has been disclosed. It will be recognized, however, that the disclosed emodiment merely illustrates the principles of this invention and many other embodiments will readily occur to others skilled in the art which will fall within the scope of the invention.

What is claimed is:

1. A switching device comprising:

a frame;

a plurality of select units mounted on said frame, each of said select units including a plurality of select magnet assemblies, a plurality of select bars, and a plurality of operators, each select bar being arranged to rotate a group of said operators from a rest position to one of two operate positions in response to activation by one of said select magnet assemblies; and

a plurality of unitary hold units mounted on said frame in operative relationship to said select units, each of said hold units including a plurality of contact sets, a plurality of cards, a plurality of mounting posts, an armature, and a plurality of generally U- shaped fingers each having two free ends joined to the bight thereof by intermediate parts, each contact set including a plurality of contacts, each card being arranged to activate a contact set in response to armature movement when said card is preconditioned for operation by a finger and each finger having said bight end attached to one of said mounting posts, one of said intermediate parts being arranged to precondition one of two cards for operation in response to rotation of an operator to one position, the other of said intermediate parts being arranged to precondition the other of said two cards for operation in response to rotation of said operator to its alternate position and said two free ends being disposed on opposite sides of an operator.

2. A switching device in accordance with claim 1 wherein the free ends of each finger are pretensioned together and each finger is deformed to pretension said free ends toward said armature.

3. A switching device in accordance with claim 1 wherein said contacts are normally open.

4. A switching devicein accordane with claim 1 wherein said contacts are of the wire spring type.

5. A switching device in accordance with claim 1 wherein said contacts are arranged for card release operation.

6. A switching device in accordance with claim 1 wherein said frame includes a plurality of tapped holes and a plurality of slots disposed on either side of said tapped holes to form mounting points and each of said select magnet assemblies includes a hollow bobbin, a coil Wound on said bobbin and a core mounted in said hollow bobbin, said core having one end adapted to magnetically cooperate with a select bar and the other end threaded to engage one of the tapped holes in said frame.

7. A switching device in accordance with claim 6 wherein said bobbin includes a pair of projecting ears adapted to engage two of said slots and cooperate with said core to hold and position said select magnet assembly on said frame.

8. In a switching device, the combination comprising:

a support;

a plurality of fixed contacts mounted on said support;

a first card including a plurality of slotted openings and an aperture having a shallow section and a deep section;

a second card including a plurality of slotted openings and an aperture having a shallow section and a deep section, said second card being disposed side by side with said first card;

a first group of elongated flexible contacts each having one portion fixed to said support, another portion located adjacent to one of said fixed contacts and a third portion extending through a slotted opening in said first card, said first group of contacts being arranged to interact with said fixed contacts in response to displacement of said first card;

a second group of elongaed flexible contacts each having one portion fixed to said support, another portion located adjacent to one of said fixed contacts and a third portion extending through a slotted opening in said second card, said second group of contacts being adapted to interact with said fixed contacts in response to displacement of said second card;

a post mounted on said support;

a generally U-shaped finger unit having a bight end for mounting and an open end for displacing said first and second cards when lifted, said bight end being attached to said post and said open end having one leg extending through the aperture in said first card and the other leg extending through the aperture in said second card, each of said legs being adapted to engage and displace its card when positioned in the shallow section of the aperture and to move freely when positioned in the deep section of said aperture;

an operator mounted on said support and having a portion disposed between said legs, said portion being adapted to move one leg from one aperture section to the other aperture section when rotated in one direction and to move the other leg from one aperture section to the other aperture section when rotated in the opposite direction; and

means for lifting the open end of said finger unit.

9. A switching device in accordance with claim 8 wherein said first and second cards are positioned with said deep sections adjacent and said shallow sections spaced apart.

10. A switching device in accordance with claim 8 wherein said movable contacts are of the wire spring type.

11. A switching device in accordance with claim 8 wherein each leg of said finger unit is doubly deformed with two biasing bends.

12. In a contact assembly for use in a crossbar switch, the combination comprising:

a hold magnet assembly including a plurality of finger units, an armature, a hold magnet, a stop bracket for positioning said armature with respect to said hold magnet, and a support member for holding said finger units, said armature, said hold magnet and said stop bracket in a unitary assembly;

a unitary fixed contact assembly removably mounted on said support member, said fixed contact assembly including a plurality of contacts; and

a movable contact assembly mounted on said support member, said movable Contact assembly comprising a plurality of cards responsive to movement of said armature, a plurality of flexible contacts adapted to engage the contacts on said fixed contact assembly in response to card movement, a clamp and a pair of balance springs, said clamp including means for positioning said flexible contacts opposite the contacts on said fixed contact assembly, said cards being adapted to receive said flexible contacts and portions of said finger units, and said pair of balance springs being deformed to bias said cards toward a predetermined position.

13. The combination in accordance with claim 12 wherein said flexible contacts are disposed between said balance springs, said cards each include an ear and a slot, and said balance springs include holes and notches for engaging the ears and slots in said cards.

14. The combination in accordance with claim 12 wherein said fixed contact assembly comprises a plurality of terminal bars, a pair of support blocks for holding said terminal bars in spaced parallel planar relationship and a pair of clamps for holding said terminal bars and said support blocks in a unitary assembly and for detachably mounting said unitary assembly on said support member.

15. The combination in accordance with claim 14 wherein each terminal bar comprises a flat strip of electrically conducting material having a loop at one end and discrete contacts distributed along one side.

16. The combination in accordance with claim 12 wherein said support member includes a mounting pin and said stop bracket includes an opening and two arms, said opening being adapted to receive said pin and said two arms being adapted to locate said armature on said support member and to regulate armature travel, respectively.

17. The combination in accordance with claim 16 wherein said arm adapted to locate said armature is symmetrically disposed along a line passing centrally across the diameter of said opening.

18. The combination in accordance with claim 12 wherein each of said cards has a boss on one end to engage one of said balance springs, an aperture adjacent to the other end to accommodate a portion of a finger unit and intermediate openings to accommodate a plurality of flexible contacts.

19. The combination in accordance with claim 18 wherein said flexible contacts are wire springs and each 0t said openings is slotted to accommodate a pair of said wire springs.

20. The combination in accordance with claim 18 wherein one of said openings is adapted to accommodate the other of said balance springs.

21. In a switching device including multiple contacts collected into a plurality of crosspoints, select units for preconditioning a particular crosspoint for operation and hold units for operating said preconditioned crosspoint, the improvement comprising a plurality of generally U-shaped finger units, a plurality of cards and a plurality of operators, each of said 'finger units being rotatably mounted on a hold unit, each of said cards having an aperture for accommodating one leg of a finger unit and a plurality of openings for collecting a plurality of contacts into a crosspoint, and said operators being mounted on said select units and adapted to selectively engage said finger units and cards in operative relationship.

22. A switching device in accordance with claim 21 wherein the bight end of each U-shaped finger is rotatably attached to a hold unit, the open end straddles an operator and the intermediate parts of each leg extend through an aperture to engage a card.

23. A switching device in accordance with claim 21 wherein said fingers are each deformed with two biasing bends, one urging the legs together at the open end and the other urging the legs toward a preselected position in said apertures.

References Cited UNITED STATES PATENTS 2,113,215 4/1938 Magrath 200l77 2,917,587 12/1959 Graybill 335-412 3,364,447 l/l968 Peek 335-112 3,369,203 2/1968 Rea 3351 12 BERNARD A. GILHEANY, Primary Examiner.

H. BROOME, Assistant Examiner.

US. Cl. X.R. 335l34 

